Hitherto, if a plurality of electromagnetic valves is used as one unit, the plurality of electromagnetic valves is mounted on a manifold, whereby a manifold electromagnetic valve is obtained, in general. In such a case, to efficiently mount as many electromagnetic valves as possible on a manifold, two electromagnetic valves arranged face to face are paired, and a plurality of such pairs of electromagnetic valves are arranged side by side on a manifold, as disclosed by, for example, PTL 1. Thus, the length of such a manifold electromagnetic valve can be reduced to about half the length of the same number of electromagnetic valves that are arranged side by side in one line on a manifold.
However, a pair of electromagnetic valves that are arranged face to face projects by a large length from the manifold in the width direction. Therefore, the width of a manifold electromagnetic valve tends to be large, leading to a problem in that, for example, it is difficult to place such a manifold electromagnetic valve if the site for placing the valve is limited.
Although the electromagnetic valve disclosed by PTL 1 is a 3-port valve, the above problem also applies to 4-port valves. A 4-port valve has a greater number of ports and has a correspondingly longer valve body than a 3-port valve. Therefore, a pair of 4-port valves that are arranged face to face has a longer total length than a pair of 3-port valves that are arranged face to face, further increasing the size of the manifold electromagnetic valve.